1. Field of the Invention
The present invention relates to a radio receiving method and apparatus for receiving a radio modulation signal of a PSK (Phase Shift Keying) system.
2. Description of the Related Art
Conventionally, a PSK system is known as one of modulation techniques used to communicate a digital signal by radio. In the PSK system, two values of a digital signal are represented with phase data of a modulation signal, and, for example, if the number of modulation phases is 2M, then a digital signal of M bits can be communicated by radio at a time.
As a radio communication apparatus in which such a PSK system as described above is used for communication by radio, for example, a digital cellular apparatus is available. A digital cellular apparatus corresponds to an apparatus wherein a radio transmission apparatus and a radio receiving apparatus of a PSK system are integrated with each other, and receives a radio modulation signal of a PSK system transmitted from a base station, demodulates the modulation signal into an audio signal and outputs the audio signal. Further, it modulates an audio signal inputted thereto into a modulation signal of a PSK system and transmits it by radio to the base station.
In a digital cellular apparatus at present, the xcfx80/4 shift QPSK is adopted as the modulation system for a modulation signal. According to the xcfx80/4 shift QPSK, a phase variation is shifted by xcfx80/4 from that of the QPSK wherein phase modulation is performed at intervals of 90 degrees and digital data of 2 bits are represented by four points on a complex plane. Since a modulation signal does not pass the origin of the complex plane as seen in FIGS. 17 and 18, fluctuation of envelope values is reduced.
However, with a digital cellular apparatus which is carried by and moved with a user, when it receives by radio and demodulates a modulation signal of the PSK system transmitted thereto, by a multi-path effect arising from reflections of radio waves from buildings therearound or a Doppler effect arising from movement of the apparatus itself, the frequency of the modulation signal which originally is fixed is fluctuated.
Therefore, in a digital cellular apparatus or the like, it is necessary to adjust the reception frequency of a modulation signal. When the reception frequency is to be adjusted in this manner, in a popular digital cellular apparatus, a radio modulation signal received once by a communication antenna is converted into an I/F signal of a predetermined frequency by an IF amplifier, and a rising edge of the I/F signal is detected by an edge detection circuit.
Such rising edges are counted by a counter circuit in response to a reference clock of a reference oscillator, and phase data is detected from the modulation signal in a cycle of a symbol clock by a register circuit based on a result of the counting. An error of the phase data is sampled out in the cycle of the symbol clock and cumulatively added for an interval of a period of a time slot, and the reference clock of the reference oscillator is varied by a PLL (Phase Locked Loop) circuit so that the phase error cumulatively added in this manner may converge within a predetermined allowance range to adjust the reception frequency.
After the adjustment of the reference frequency of the modulation signal is completed in such a manner as described above, frame synchronization of the modulation signal should subsequently be established. In this instance, since, in the modulation signal, predetermined bit data is contained at a predetermined position of a frame, the predetermined bit data is detected from the received modulation signal to establish frame synchronization.
More particularly, first bit data and second bit data are sampled out for each frame in a cycle of the symbol clock from the modulation signal first, and then a frame correlation value is calculated from the first bit data while CRC calculation is executed with the second bit data. Then, frame synchronization is established in response to results of the calculation.
After the adjustment of the reception frequency is completed and frame synchronization of the modulation signal is established in such a manner as described above, since a condition wherein phase data can be detected well from the received radio modulation signal is reached, the phase of the received radio modulation signal can be demodulated into a digital signal to reproduce a speech signal and so forth.
It is to be noted that some of digital cellular apparatus at present apply a diversity system for such radio reception of a modulation signal as described above. In a digital cellular apparatus which adopts this diversity system, a pair of communication antennae are arranged in a predetermined spaced relationship from each other and a radio modulation signal is received by the communication antennae. Electric field strengths of ratio reception of the communication antennae are detected individually, and one of the communication antennae which exhibits a higher one of the electric field strengths is used for radio reception of the apparatus.
While such a digital cellular apparatus or the like as described above can receive and demodulate a radio modulation signal of a PSK system transmitted thereto by radio, radio receiving apparatus at present have various disadvantages.
For example, while the digital cellular apparatus or the like samples out and cumulatively adds the phase error of a modulation signal in a cycle of a symbol clock upon starting of radio communication in order to adjust the reception frequency of the modulation signal as described above, this complicates processing for the calculation of the phase error. Further, if the reception condition deteriorates in the proximity of a sampling timing, then a result of the sampling becomes noise, and consequently, the speed until the adjustment of the reception frequency is completed drops.
Further, while the digital cellular apparatus or the like samples out, in order to establish frame synchronization, bit data for each frame in the cycle of the symbol clock from the modulation signal and executes calculation of a frame correlation value and CRC calculation, also this drops the speed in which frame synchronization is established if the reception condition deteriorates in the proximity of a sampling timing.
Particularly, while the adjustment of the reception frequency is repeated in a predetermined cycle, at a point of time when frame synchronization is established, a phase error is sampled out from the modulation signal at a particular timing corresponding to a synchronizing frame. Accordingly, if the sampling timing is in the proximity of a phase variation of the modulation signal, then it is difficult to detect the phase error well and the reception performance is deteriorated.
With a digital cellular apparatus at present, it is prescribed to adjust the reception frequency until the frequency deviation becomes smaller than 0.3 ppm (part per million). However, in order to realize this, a reference oscillator is required to have a highly stable output frequency, and this drops the productivity of digital cellular apparatus.
In order to overcome the disadvantage just described, it is a common practice to perform AFC (Automatic Frequency Control) processing for detection data of a phase error to produce digital data of a plurality of bits, convert the digital data into analog data and input resulting data to a TCXO (Temperature Compensated Crystal Oscillator) of the VC (Voltage Controlled) type so that the frequency of a reference clock to be outputted from the TCXO of the VC type is adjusted with a high degree of accuracy.
However, with a conventional digital cellular apparatus, adjustment of the reception frequency with the reference clock adjusted in this manner is executed fully even at a point of time before frame synchronization is established immediately after operation of the apparatus is started. Consequently, high grade data processing is executed even from a point of time at which no such processing is required. Consequently, the burden of adjustment of the reception frequency is increased idly and the speed is dropped.
Further, in a popular digital cellular apparatus, as described above, a received radio modulation signal is converted into an I/F signal of a predetermined signal first, and then rising edges are counted in response to a reference clock, whereafter phase data is detected from the modulation signal and adjustment of the reception frequency, establishment of frame synchronization and so forth are executed.
Further, while, in a conventional digital cellular apparatus, the frequencies of a reference clock of a reference oscillator and an intermediate frequency of an I/F amplifier are different depending upon the specifications of products, if the ratios of the intermediate frequency of the I/F amplifier and the symbol clock of the modulation signal are not equal to integral numbers of times that of the reference clock, then an error occurs with a detection signal of a phase error and so forth.
Consequently, a reference clock and an intermediate frequency are conventionally set in response to a symbol clock of a modulation signal. However, this lowers the degree of freedom of a device which can be used as the reference oscillator or the I/F amplifier and deteriorates the total productivity where a large number of types of digital cellular apparatus are produced.
Further, while a product of a digital cellular apparatus which adopts a diversity system as described above is available, with such a digital cellular apparatus as just described, since one of a pair of communication antennae is selectively used in response to an electric field strength, for example, in a case wherein the electric field strength is high due to noise, that one of the communication antennae which is not suitable because of the noise is selected.
In order to eliminate the disadvantage just described, also a system wherein a pair of reception signals are diversity composed in response to a ratio of electric field strengths of radio reception of a pair of communication antennae has been proposed. However, a detailed technique which realizes the system appropriately with a practical structure has not been proposed as yet.
It is an object of the present invention to provide a radio receiving method and apparatus by which adjustment of a reception frequency can be completed at a high speed without requiring a reference clock whose oscillation frequency is extremely high.
It is another object of the present invention to provide a radio receiving method and apparatus by which frame synchronization can be established at a high speed even when a reception condition is bad.
It is a further object of the present invention to provide a radio receiving method and apparatus by which a reception performance of a modulation signal is good.
It is a still further object of the present invention to provide a radio receiving method and apparatus wherein the degree of freedom of an intermediate frequency of an I/F amplifier or a reference clock of a reference oscillator is good.
It is a yet further object of the present invention to provide a radio receiving method and apparatus by which a technique of diversity composing a pair of reception signals in response to a ratio between electric field strengths of radio reception of a pair of communication antennae can be realized.
It is an additional object of the present invention to provide a method of setting a correction parameter to a radio receiving method and apparatus wherein the cycle of a reference clock of a reference oscillator need not be changed even if the cycle of a signal output of an I/F amplifier is changed.
In order to attain the object described above, according to an aspect of the present invention, there is provided a radio receiving method wherein a radio modulation signal of a PSK system transmitted by radio with a predetermined frequency is received and the reception frequency of the modulation signal is adjusted to a transmission frequency, comprising the steps of receiving a radio modulation signal of the PSK system at random, producing a sampling clock of a predetermined frequency, sampling out phase data out from the received radio modulation signal in a cycle of the sampling clock, cumulatively adding the phase data thus sampled out for a predetermined period, and adjusting the reception frequency so that a calculation result of the cumulative addition may satisfy a predetermined allowance range. In the radio receiving method, the reception frequency of a received radio modulation signal can be adjusted by simple processing without detecting a phase error from the received radio modulation signal.
It is to be noted that the modulation signal in the present invention permits various radio signals of various numbers of phases modulated by a PSK system and permits, for example, a modulation signal of a xcfx80/4 shift QPSK system. Further, the phase data of a modulation signal in the present invention is a general term for various data relating to a phase of a modulation signal and permits, for example, analog or digital data representing a phase variation amount, a phase difference, a phase itself or the like.
The radio receiving method may be constructed such that the sampling clock is produced so as to have a cycle equal to a fraction of that of a symbol clock of the modulation signal, and the phase data is sampled out from the modulation signal in the cycle of the sampling clock. In the radio receiving method, sampling out of the phase data of the modulation signal is performed at a timing of a cycle equal to a fraction of that of the symbol clock, that is, the cycle of the phase variation, of the modulation signal. Consequently, adjustment of the reception frequency can be completed at a high speed. Besides, in order to realize this, it is not necessary to produce a sampling clock from a reference clock which is stable with a high degree of accuracy.
The radio receiving method may be further constructed such that the modulation system of the modulation signal is a xcfx80/4 shift QPSK system, and the sampling clock is produced so as to have a cycle equal to one fourth that of the symbol clock of the modulation signal. In the radio receiving method, since the sampling clock which has a cycle equal to one fourth that of the symbol clock of the modulation signal whose modulation system is a xcfx80/4 shift QPSK system is produced, the modulation signal of the xcfx80/4 shift QPSK system can be sampled at a timing optimum to adjustment of the reception frequency by accumulation of the phase data.
According to another aspect of the present invention, there is provided a radio receiving method wherein a radio modulation signal of a PSK system transmitted with predetermined bit data contained at a predetermined position of a frame is received and the predetermined bit data is detected from the received radio modulation signal to establish frame synchronization, comprising the steps of receiving a radio modulation signal of the PSK system, producing a sampling clock of a cycle equal to a fraction of that of the received radio modulation signal, sampling out the predetermined bit data in the period of the sampling clock from the received radio modulation signal, and establishing frame synchronization in response to the sampled out bit data. In the radio receiving method, establishment of frame synchronization is executed with bit data sampled out at a timing of a cycle equal to a fraction of that of the symbol clock, that is, the cycle of the phase variation, of the modulation signal. In other word, bit data to be utilized for establishment of frame synchronization can be sampled out at a timing of a cycle equal to a fraction of that of the phase variation. Consequently, establishment of frame synchronization can be performed at a high speed.
According to a further aspect of the present invention, there is provided a radio receiving method wherein a radio modulation signal of a PSK system transmitted with predetermined bit data contained at a predetermined position of a frame is received and the predetermined bit data is detected from the received radio modulation signal to establish frame synchronization, comprising the steps of receiving a radio modulation signal of the PSK system, producing a sampling clock of a cycle equal to a fraction of that of the received radio modulation signal, sampling out first bit data in the cycle of the sample clock from the received radio modulation signal, calculating a frame correlation value from the sampled out first bit data, sampling out second bit data in the cycle of the sampling clock from the modulation signal, executing CRC calculation with the sampled out second bit data and second bit data set in advance, and establishing frame synchronization in response to the frame correlation value and a result of the CRC calculation. In the radio receiving method, first and second bit data to be utilized for calculation of a frame correlation value and CRC calculation are sampled out at a timing of a cycle equal to a fraction of that of the phase variation of the modulation signal. Consequently, establishment of frame synchronization can be completed at a high speed.
According to a still further aspect of the present invention, there is provided a radio receiving method wherein a radio modulation signal of a PSK system transmitted with a predetermined frequency is received and a phase error between radio transmission and radio reception of the modulation signal is detected, and then the received radio modulation signal is synchronously demodulated based on the phase error, comprising the steps of receiving a radio modulation signal of the PSK system, producing a sampling clock of a cycle equal to a fraction of that of the received modulation signal, detecting a phase error in the cycle of the sampling clock from the received radio modulation signal, cumulatively adding the phase error thus detected for a predetermined period, and setting a detection timing of the phase error at which a calculation result of the cumulative addition becomes minimum. In the radio receiving method, since a detection timing of the phase error at which a calculation result of the cumulative addition becomes minimum is set, after this setting is performed, a phase error of the modulation signal is detected at a detection timing at which a calculation result of the cumulative addition becomes minimum. Consequently, it is prevented that the phase error of the modulation signal is detected at a timing at which it increases because of an influence of the phase variation or the like. Accordingly, the phase error can be detected at an optimum timing and the reception performance of the modulation signal can be improved.
According to a yet further aspect of the present invention, there is provided a radio receiving method wherein a radio modulation signal of a PSK system transmitted with a predetermined frequency is received and a phase error between radio transmission and radio reception of the modulation signal is detected, and then the received radio modulation signal is synchronously demodulated based on the phase error, comprising the steps of receiving a modulation signal of the PSK system, producing a sampling clock of a cycle equal to a fraction of that of the received radio modulation signal, detecting a phase error in the cycle of the sampling clock from the received radio modulation signal, cumulatively adding the phase error thus detected for a predetermined period, and synchronously demodulating the modulation signal with the cumulatively added phase error. In the radio receiving method, synchronous demodulation is executed based on the phase error sampled out at a timing of a cycle equal to a fraction of that of the phase variation of the modulation signal. Thus, since the phase error to be utilized for synchronous demodulation of the modulation signal can be sampled out at a timing of a cycle equal to a fraction of that of the phase variation, synchronous demodulation of the modulation signal can be completed at a high speed.
According a yet further aspect of the present invention, there is provided a radio receiving method wherein a radio modulation signal of a PSK system transmitted with a predetermined frequency is received and a phase error between radio transmission and radio reception of the modulation signal is detected, and then the received radio modulation signal is synchronously demodulated based on the phase error, comprising the steps of receiving a radio modulation signal of the PSK system, producing a sampling clock of a cycle equal to a fraction of that of the received radio modulation signal, detecting a phase error in the cycle of the sampling clock from the received radio modulation signal, cumulatively the phase error thus detected for a predetermined period, setting a detecting timing of the phase error at which the cumulatively added phase error becomes minimum, and synchronously demodulating the modulation signal with the phase error detected at the set timing and cumulatively added. In the radio receiving method, since the phase error is detected at a timing at which a result of the accumulation of the phase error which is sampled out at a timing of a cycle equal to a fraction of that of the symbol clock becomes minimum, the phase error is prevented from being detected at a timing at which it increases because of an influence of the phase variation or the like. Further, since the phase error to be utilized for synchronous demodulation of the modulation signal can be sampled out at a timing of a cycle equal to a fraction of that of the phase variation, synchronous demodulation of the modulation signal can be completed at a high speed and the reception performance of the modulation signal can be improved.
Preferably, the radio receiving methods are constructed such that the modulation system of the modulation signal is a xcfx80/4 shift QPSK system, and the sampling clock is produced in a cycle equal to one eighth that of a symbol clock of the modulation signal. In the radio receiving method, since the sampling clock whose cycle is one eighth that of the symbol clock of the modulation signal whose modulation system is a xcfx80/4 shift QPSK system is produced, the modulation signal of the xcfx80/4 shift QPSK system can be sampled at an optimum timing.
According to a yet further aspect of the present invention, there is provided a radio receiving method wherein a radio modulation signal of a PSK system transmitted with a predetermined frequency is received and phase data is differentially detected from the modulation signal, comprising the steps of receiving a radio modulation signal of the PSK system, producing a sampling clock of a cycle equal to a fraction of that of the received radio modulation signal, differentially detecting phase data in the cycle of the sampling clock from the received radio modulation signal, and removing bit data set in advance from the differentially detected phase data. In the radio receiving method, an effective part of the modulation signal can be extracted from the differentially detected phase data, and consequently, the phase data of the modulation signal can be adjusted to an optimum dynamic range.
According to a yet further aspect of the present invention, there is provided a radio receiving method wherein a radio modulation signal of a PSK system transmitted with a predetermined frequency is received and phase data of the modulation signal is detected, comprising the steps of receiving a radio modulation signal of the PSK system, converting the received radio modulation signal into an intermediate frequency signal of a predetermined cycle, producing a reference clock of a predetermined cycle, producing a sampling clock of a cycle equal to a fraction of that of the reference signal from the reference clock, detecting phase data in the cycle of the sampling clock from the intermediate frequency signal, and correcting the phase data with a correction parameter corresponding to frequency differences among the symbol clock of the modulation signal, the intermediate frequency signal, the reference clock and the sampling clock. In the radio receiving method, an offset which occurs with a result of detection of the phase error from cycle differences among the symbol clock of the modulation signal, the intermediate frequency signal, the reference clock and the sampling clock is corrected. Consequently, the reception performance of the modulation signal can be improved and the intermediate frequency signal and the reference clock can be varied freely.
The radio receiving method may be constructed such that one of a plurality of kinds of sampling clocks having cycles equal to fractions of that of the symbol clock is switchably produced at a ratio corresponding to the modulation system of the modulation signal, and one of a plurality of kinds of correction parameters set in advance is selectively used in response to switching of the sampling clocks. In the radio receiving method, the modulation signal is sampled at an optimum timing corresponding to the modulation system of the same, and even if the sampling clock is switched to another sampling clock, an offset of a result of detection of the phase error is corrected appropriately by switching of the correction parameter corresponding to the switching of the sampling clock.
Preferably, the modulation system of the modulation signal is a xcfx80/4 shift QPSK system, and one of a plurality of sampling clocks having frequencies equal to one fourth and one eighth that of the symbol clock of the modulation signal is selectively produced. In the radio receiving method, since the sampling clock whose cycle is one eighth that of the symbol clock of the modulation signal whose modulation system is a xcfx80/4 shift QPSK system is produced, the modulation signal of the xcfx80/4 shift QPSK system can be sampled at an optimum timing. Consequently, even if the sampling clock is switched, a result of detection of the phase error can be corrected appropriately.
According to a yet further aspect of the present invention, there is provided a radio receiving method, comprising the steps of registering a plurality of diversity ratios in advance, receiving a radio signal by a pair of communication antennae, converting electric field strengths of radio reception of the pair of communication antennae individually from analog into digital data, calculating difference data from the pair of digital data, reading out one of the diversity ratios registered in advance using the calculated difference data as address data, and diversity composing the pair of received radio signals in response to the read out diversity ratio. In the radio receiving method, radio signals received by the pair of communication antennae are diversity composed at an appropriate diversity ratio in response to a difference in electric field strength. Consequently, the reception performance of the radio signal can be improved.
According to a yet further aspect of the present invention, there is provided a radio receiving apparatus which receives a radio modulation signal of a PSK system transmitted with a predetermined frequency and adjusts a reception frequency of the modulation signal corresponding to a transmission frequency, comprising radio reception means for random receiving a radio modulation signal of the PSK system, clock production means for producing a sampling clock of a predetermined cycle, phase sampling means for sampling out phase data in the cycle of the sampling clock produced by the clock production means from the modulation signal received by the radio reception means, phase accumulation means for cumulatively adding the phase data sampled out by the phase sampling means for a predetermined period, and reception adjustment means for adjusting a reception frequency so that a calculation result of the cumulative addition of the phase accumulation means may satisfy a predetermined allowance range.
In the radio receiving apparatus, a modulation signal of the PSK system is received at random by the radio reception means, and a sampling clock of a predetermined frequency is produced by the clock production means. Then, phase data is sampled out from the received radio modulation signal in a cycle of the sampling clock. The phase data thus sampled out is cumulatively added for a predetermined period, and the reception frequency is adjusted by the reception adjustment means so that a calculation result of the cumulative addition may satisfy a predetermined allowance range. Consequently, the reception frequency of a received radio modulation signal can be adjusted without detecting a phase error from the received radio modulation signal.
It is to be noted that the individual components in the present invention are required only to be constructed so as to realize the functions required therefor and allow, for example, hardware for exclusive use, a computer to which appropriate functions are provided by a program, functions realized in the inside of a computer by an appropriate program, and any combination of them.
The radio receiving apparatus may be constructed such that the clock production means produces a sampling clock of a cycle equal to a fraction of that of a symbol clock of the modulation signal, and the phase sampling means samples out the phase data from the modulation signal in the cycle of the sampling clock produced by the clock production means.
In the radio receiving apparatus, the sampling clock is produced by the clock production means so as to have a cycle equal to a fraction of that of the symbol clock of the modulation signal, and the phase data is sampled out from the modulation signal in the cycle of the sampling clock by the phase sampling means. Accordingly, sampling out of the phase data of the modulation signal is performed at a timing of a cycle equal to a fraction of that of the symbol clock, that is, the period of the phase variation, of the modulation signal. Consequently, adjustment of the reception frequency can be completed at a high speed. Besides, in order to realize this, it is not necessary to produce a sampling clock from a reference clock which is stable with a high degree of accuracy. Consequently, the productivity of the radio receiving apparatus can be improved.
The radio receiving apparatus may be further constructed such that the clock production means produces a sampling clock of a cycle equal to a fraction of that of the symbol clock at a ratio corresponding to the modulation system of the modulation signal. In the radio receiving apparatus, a sampling clock is produced with a cycle equal to a fraction of that of the symbol clock at a ratio corresponding to the modulation system of the modulation signal by the clock production means. Consequently, a sampling clock can be produced with a cycle optimum to the modulation system of the modulation signal.
The radio receiving apparatus may be further constructed such that the modulation system of the modulation signal is a xcfx80/4 shift QPSK system, and the clock production means produces a sampling clock of a cycle equal to one fourth that of the symbol clock of the modulation signal. In the radio receiving apparatus, since the sampling clock which has a cycle equal to one fourth that of the symbol clock of the modulation signal whose modulation system is a xcfx80/4 shift QPSK system is produced, phase data is sampled out in a cycle equal to one fourth that of the symbol clock of the modulation signal from the modulation signal of the xcfx80/4 shift QPSK system. Consequently, the modulation signal of the xcfx80/4 shift QPSK system can be sampled at a timing optimum to adjustment of the reception frequency by accumulation of the phase data.
According to a yet further aspect of the present invention, there is provided a radio receiving apparatus wherein a radio modulation signal of a PSK system transmitted with predetermined bit data contained at a predetermined position of a frame is received and the predetermined bit data is detected from the received radio modulation signal to establish frame synchronization, comprising radio reception means for radio receiving a radio modulation signal of the PSK system, clock production means for producing a sampling clock of a cycle equal to a fraction of that of a symbol clock of the modulation signal received by the radio reception means, bit sampling means for sampling out predetermined bit data from the radio signal received by the radio reception means in the cycle of the sampling clock produced by the clock production means, and frame synchronization means for establishing frame synchronization corresponding to the bit data sampled out by the bit sampling means.
In the radio receiving apparatus, a radio modulation signal of the PSK system is received by the radio reception means, and a sampling clock of a cycle equal to a fraction of that of the received radio modulation signal is produced by the clock production means. Then, the predetermined bit data is sampled out in the period of the sampling clock from the received radio modulation signal by the bit sampling means, and frame synchronization is established corresponding to the sampled out bit data by the frame synchronization means. Consequently, establishment of frame synchronization is executed with bit data sampled out at a timing of a cycle equal to a fraction of that of the symbol clock, that is, the cycle of the phase variation, of the modulation signal. In other word, bit data to be utilized for establishment of frame synchronization can be sampled out at a timing of a cycle equal to a fraction of that of the phase variation. Consequently, establishment of frame synchronization can be performed at a high speed.
The radio receiving apparatus may be constructed such that the bit sampling means samples out first bit data and second bit data from the modulation signal in the cycle of the sampling clock, and the frame synchronization means calculates a frame correlation value from the sampled out first bit data, executes CRC calculation with the second bit data, and establishes frame synchronization corresponding to the frame correlation value and a result of the CRC calculation.
In the radio receiving apparatus, when first bit data is sampled out in the cycle of the sampling clock from the modulation signal by the bit sampling means, a frame correlation value is calculated from the thus sampled out first bit data by the frame synchronization means. Then, since second bit data is sampled out in the period of the sampling clock from the modulation signal by the bit sampling means, CRC calculation is executed with the thus sampled out second bit data by the frame synchronization means, and frame synchronization is established corresponding to the frame correlation value and a result of the CRC calculation. Consequently, sampling out of first and second bit data to be utilized for calculation of a frame correlation value and CRC calculation is executed at a timing of a cycle equal to a fraction of that of the phase variation of the modulation signal. As a result, establishment of frame synchronization can be completed at a high speed.
According to a yet further aspect of the present invention, there is provided a radio receiving apparatus wherein a radio modulation signal of a PSK system transmitted with a predetermined frequency is received and a phase error between radio transmission and radio reception of the modulation signal, and then the received radio modulation signal is synchronously demodulated based on the phase error, comprising radio reception means for receiving a radio modulation signal of the PSK system, clock production means for producing a sampling clock of a cycle equal to a fraction of that of a symbol clock of the modulation signal received by the radio reception means, error detection means for detecting a phase error in the cycle of the sampling clock produced by the clock production means from the modulation signal received by the radio reception means, error accumulation means for cumulatively adding the phase error detected by the error detection means for a predetermined period, and timing control means for setting a detection timing of the phase error at which a calculation result of the cumulative addition by the error accumulation means becomes minimum to the error detection means.
In the radio receiving apparatus, a radio modulation signal of the PSK system is received by the radio reception means, and a sampling clock of a cycle equal to a fraction of that of the received radio modulation signal is produced by the clock production means. Then, a phase error is detected in the cycle of the sampling clock from the received radio modulation signal by the error detection means. The phase error thus detected is cumulatively added for a predetermined period by the error accumulation means, and a detection timing of the phase error at which a calculation result of the cumulative addition becomes minimum is set to the error detection means by the timing control means. Consequently, since a detection timing of the phase error at which a calculation result of the cumulative addition becomes minimum is set to the error detection means, after this setting is performed, a phase error of the modulation signal is detected at a detection timing at which a calculation result of the cumulative addition becomes minimum. Consequently, it is prevented that the phase error of the modulation signal is detected at a timing at which it increases because of an influence of the phase variation or the like. Accordingly, the phase error can be detected at an optimum timing and the reception performance of the modulation signal can be improved.
According to a yet further aspect of the present invention, there is provided a radio receiving apparatus wherein a radio modulation signal of a PSK system transmitted with a predetermined frequency is received and a phase error between radio transmission and radio reception of the modulation signal is detected, and then the received radio modulation signal is synchronously demodulated based on the phase error, comprising radio reception means for receiving a radio modulation signal of the PSK system, clock production means for producing a sampling clock of a cycle equal to a fraction of that of a symbol clock of the modulation signal received by the radio reception means, error detection means for detecting a phase error in the cycle of the sampling clock produced by the clock production means from the modulation signal received by the radio reception means, error accumulation means for cumulatively adding the phase error detected by the error detection means for a predetermined period, and synchronous demodulation means for synchronously demodulating the modulation signal with the phase error cumulatively added by the error accumulation means.
In the radio receiving apparatus, a radio modulation signal of the PSK system is received by the radio reception means, and a sampling clock of a cycle equal to a fraction of that of the received radio modulation signal is produced by the clock production means. Then, a phase error is detected in the cycle of the sampling clock from the received radio modulation signal by the error detection means. Further, the phase error thus detected is cumulatively added for a predetermined period by the error accumulation means, and the modulation signal is synchronously demodulated with the cumulatively added phase error by the synchronous demodulation means. Consequently, synchronous demodulation is executed based on the phase error sampled out at a timing of a cycle equal to a fraction of that of the phase variation of the modulation signal. Thus, since the phase error to be utilized for synchronous demodulation of the modulation signal can be sampled out at a timing of a cycle equal to a fraction of that of the phase variation, synchronous demodulation of the modulation signal can be completed at a high speed.
According to a yet further aspect of the present invention, there is provided a radio receiving apparatus wherein a radio modulation signal of a PSK system transmitted with a predetermined frequency is received and a phase error between radio transmission and radio reception of the modulation signal is detected, and then the received radio modulation signal is synchronously demodulated based on the phase error, comprising radio reception means for receiving a radio modulation signal of the PSK system, clock production means for producing a sampling clock of a cycle equal to a fraction of that of a symbol clock of the modulation signal received by the radio reception means, error detection means for detecting a phase error in the cycle of the sampling clock produced by the clock production means from the modulation signal received by the radio reception means, error accumulation means for cumulatively adding the phase error detected by the error detection means for a predetermined period, timing control means for setting a detection timing of the phase error at which the cumulatively added phase error of the error accumulation means becomes minimum to the error detection means, and synchronous demodulation means for synchronously demodulating the modulation signal with the phase error detected by the error detection means at the timing set by the timing control means and cumulatively added by the error accumulation means.
In the radio receiving apparatus, a radio modulation signal of the PSK system is received by the radio reception means, and a sampling clock of a cycle equal to a fraction of that of the received radio modulation signal is produced by the clock production means. Further, a phase error is detected in the cycle of the sampling clock from the received radio modulation signal by the error detection means. The phase error thus detected is cumulatively added for a predetermined period by the error accumulation means, and a detecting timing of the phase error at which the cumulatively added phase error becomes minimum is set to the error detection means by the timing control means. After this setting is performed, the phase error is detected at the set timing by the error detection means. The phase error detected at this timing is cumulatively added for a predetermined period by the error accumulation means, and the modulation signal is synchronously demodulated with the cumulatively added phase error by the synchronous demodulation means. Consequently, synchronous demodulation is executed based on the phase error which is sampled out at a timing of a cycle equal to a fraction of that of the phase variation of the modulation signal. Since the phase error is detected at a timing at which a result of the accumulation of the phase error which is sampled out at a timing of a cycle equal to a fraction of that of the symbol clock becomes minimum, the phase error is prevented from being detected at a timing at which it increases because of an influence of the phase variation or the like. Further, since the phase error to be utilized for synchronization of the modulation signal can be sampled out at a timing of a cycle equal to a fraction of that of the phase variation, synchronous demodulation of the modulation signal can be completed at a high speed and the reception performance of the modulation signal can be improved.
The radio receiving apparatus may be constructed such that the clock production means produces a sampling clock of a cycle equal to a fraction of that of the symbol clock at a ratio corresponding to the modulation system of the modulation signal. In the radio receiving apparatus, a sampling clock of a cycle equal to a fraction of that of the symbol clock is produced at a ratio corresponding to the modulation system of the modulation signal by the clock production means. Consequently, the modulation signal can be sampled at a timing optimum to the modulation system.
Preferably, the radio receiving apparatus are constructed such that the modulation system of the modulation signal is a xcfx80/4 shift QPSK system, and the clock production means produces a sampling clock of a cycle equal to one eighth that of the symbol clock of the modulation signal. In the radio receiving apparatus, since the sampling clock whose cycle is one eighth that of the symbol clock of the modulation signal whose modulation system is a xcfx80/4 shift QPSK system is produced, the modulation signal of the xcfx80/4 shift QPSK system can be sampled at an optimum timing.
According to a yet further aspect of the present invention, there is provided a radio receiving apparatus wherein a radio modulation signal of a PSK system transmitted with a predetermined frequency is received and phase data is differentially detected from the modulation signal, comprising radio reception means for receiving a radio modulation signal of the PSK system, clock production means for producing a sampling clock of a predetermined cycle, phase detection means for differentially detecting phase data in the cycle of the sampling clock produced by the clock production means from the modulation signal received by the radio reception means, and signal adjustment means for removing bit data set in advance from the phase data differentially detected by the phase detection means.
In the radio receiving apparatus, a radio modulation signal of the PSK system is received by the radio reception means, and a sampling clock of a cycle is produced by the clock production means. Then, phase data is differentially detected in the cycle of the sampling clock from the received radio modulation signal by the phase detection means, and bit data set in advance is removed from the differentially detected phase data. Consequently, an effective part of the modulation signal can be extracted from the differentially detected phase data by the signal adjustment means, and consequently, the phase data of the modulation signal can be adjusted to an optimum dynamic range.
According to a yet further aspect of the present invention, there is provided a radio receiving apparatus wherein a radio modulation signal of a PSK system transmitted with a predetermined frequency is received and phase data is detected from the modulation signal, comprising radio reception means for receiving a radio modulation signal of the PSK system, I/F conversion means for converting the modulation signal received by the radio reception means into an intermediate frequency signal of a predetermined cycle, clock generation means for generating a reference clock of a predetermined cycle, clock production means for producing, from the reference clock generated by the clock generation means, a sampling clock of a cycle equal to a fraction of that of the reference clock, phase detection means for detecting phase data in the cycle of the sampling clock produced by the clock production means from the intermediate frequency signal outputted from the I/F conversion means, and signal correction means for correcting the phase data detected by the phase detection means with a correction parameter corresponding to frequency differences among the symbol clock of the modulation signal, the intermediate frequency signal, the reference clock and the sampling clock.
In the radio receiving apparatus, a radio modulation signal of the PSK system is received by the radio reception means, and the received radio modulation signal is converted into an intermediate frequency signal of a predetermined cycle by the I/F conversion means. A reference clock of a predetermined cycle is generated by the clock generation means, and a sampling clock of a cycle equal to a fraction of that of the reference signal is produced from the reference clock by the clock production means. Then, phase data is detected in the cycle of the sampling clock from the intermediate frequency signal by the phase detection means, and the phase data is corrected with a correction parameter corresponding to frequency differences among the symbol clock of the modulation signal, the intermediate frequency signal, the reference clock and the sampling clock by the signal correction means. Consequently, an offset which occurs with the phase data of the modulation signal from cycle differences among the clocks is corrected. Consequently, the reception performance of the modulation signal can be improved. Further, since various devices can be adopted freely for the I/F conversion means and the clock generation means, the productivity of the radio receiving apparatus can be improved.
The radio receiving apparatus may be constructed such that the clock production means selectively produces one of a plurality of kinds of sampling clocks having cycles equal to fractions of that of the symbol clock at a ratio corresponding to the modulation system of the modulation signal, and the signal correction means selectively uses one of a plurality of kinds of correction parameters set in advance in response to selective switching of the sampling clock by the clock production means.
In the radio reception apparatus, one of a plurality of kinds of sampling clocks having cycles equal to fractions of that of the symbol clock is produced at a ratio corresponding to the modulation system of the modulation signal by the clock production means, and one of a plurality of kinds of correction parameters set in advance is selectively used in response to selective switching of the sampling clocks. Accordingly, even if the sampling clock is switched to another sampling clock, an offset of the phase data of the modulation signal is corrected appropriately by switching of the correction parameter corresponding to the switching of the sampling clock.
Preferably, the radio receiving apparatus is constructed such that the modulation system of the modulation signal is a xcfx80/4 shift QPSK system, and the clock production means selectively produces one of sampling clocks having cycles equal to one fourth and one eighth that of the symbol clock of the modulation signal.
In the radio receiving apparatus, the sampling clock whose cycle is one fourth or one eighth that of the symbol clock of the modulation signal whose modulation system is a xcfx80/4 shift QPSK system is produced by the clock production means, the modulation signal of the xcfx80/4 shift QPSK system can be sampled at an optimum timing. Consequently, even if the sampling clock is switched, an offset of a result of detection of the phase error can be corrected appropriately.
According to a yet further aspect of the present invention, there is provided a radio receiving apparatus, comprising a pair of communication antennae for receiving a radio signal, a pair of A/D conversion means for converting electric field strengths of radio reception of the pair of communication antennae individually from analog to digital data, difference calculation means for calculating difference data from the pair of digital data individually from the pair of A/D conversion means, rate storage means in which a plurality of diversity ratios are registered in advance individually for predetermined address data, rate readout means for reading out one of the diversity ratios from the rate storage means using the difference data calculated by the difference calculation means as address data, and signal composition means for diversity composing the pair of radio signals received by the pair of communication antennae in response to the diversity ratio read out by the rate readout means.
In the radio receiving apparatus, a radio signal is received by the pair of communication antennae, and electric field strengths of radio reception of the pair of communication antennae are individually converted from analog into digital data by the A/D conversion means. Then, difference data is calculated from the pair of resulting digital data by the difference calculation means, and one of the diversity ratios registered in advance is read out from the rate storage means by the rate readout means using the difference data calculated by the difference calculation means as address data. Then, the radio signals received by the pair of communication antennae are diversity composed in response to the read out diversity ratio by the signal composition means. Consequently, radio signals received by the pair of communication antennae are diversity composed at an appropriate diversity ratio in response to a difference in electric field strength. Consequently, the reception performance of the radio signal can be improved.